It basically means, New World Macs. The ROMs that Macs have after the implementation of firewire are what is specified. Rather than telling you to look for your ROM revision, they just say, If you have Firewire then your OK.

Don't forget Apple sells Macs, and if you don't have firewire, well then they'd love for you to get a new Mac.

Besides, you don't want to run tiger on a 233mhz bondi iMac with 32mb RAM, or a beige G3 tower.